This may not help, since you're looking for a higher-end amp, but when I owned the Schiit Magni 2 Uber, I thought it barely got warm at all. It has more than enough power for the headphones you have. Then there's the issue of "quality" beyond sheer output power. Many people say certain high-end amps sound better, even when they have lower output power. The reasons for this are unclear, but it seems to be related to the design of the amp. Anyway, since the M2U is so cheap, I would recommend comparing it side by side with a high-end amp, to hear directly what differences there are. The only high-end amps I've used are the MOON Neo 430HA and Sennheiser HDVD 800, with the Abyss, HE1000, HE-6, and HD 800. Both amp/DACs sounded about the same to me. Although they are not listed on your profile, it seems you're also into electrostats. As I'm sure you know, those amps are a lot more complex. I believe even all the lower-end electrostatic amps (like the one I have) are Class A.